An electric motor operates by rotation of a rotor relative to a stator in response to a magnetic field generated in the stator or rotor depending on the type of motor. During a period of time when a motor is energized, a rotating rotor (for example) builds inertia. Upon deactivation of the motor, the magnetic field impetus for the rotation of the rotor collapses but the inertia developed is still present. Thus, the rotor, although slowing, continues to rotate for a short period of time.
By way of example, electric motors are used to power electric power steering (EPS) systems. In that situation, the driver of a vehicle will turn a hand wheel of a vehicle. A torque sensor detects the rotation and sends a signal to a control, which then sends a signal to an electric motor to turn on. When the electric motor begins operation, it will rotate a gear mechanism, which rotates a shaft, ultimately steering road wheels of a vehicle and thereby assisting the driver with turning the vehicle. When the driver stops steering the vehicle, the torque sensor will again send a signal to the electric motor to deactivate, thereby deactivating the EPS system. As explained above, when the motor has been deactivated, the inertia forces of the rotating rotor continue to rotate the rotor, which will continue to rotate the gear mechanism, ultimately steering the road wheels until the rotor has completely stopped moving.
Disclosed herein is a motor system including an electric motor, a shaft extending through the motor and through a magnetorheological (MR) fluid stopper, the MR fluid stopper comprising a rotor and a stator, wherein the stator is in operable communication with the rotor. In addition, an MR fluid is disposed at the rotor and the stator.
The above-described and other features and advantages of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.